TW201804356A - Magnetic stripe data transmission system and power decreasing and reliable method for transporting data - Google Patents

Abstract

A magnetic stripe data transmission (MST) driver and a method for driving the MST are disclosed. The MST driver is configured to transmit magnetic strip data comprising of streams of pulses. The MST driver comprises a pair of high side switches and a pair of low side switches. The pair of high side switches comprises a first switch and a second switch. The pair of low side switches comprises a third switch and a fourth switch. The first, second, third and fourth switches are arranged in a full bridge type configuration connected across a voltage source and a ground. An inductive coil is connected across outputs of the full bridge type configuration of the switches. The MST driver includes a switch driver configured to drive the pair of low side switches and the pair of high side switches under current slope control using pulse width modulation. The driven load current has a rising portion and a falling portion through the inductive coil in a forward direction or in a reverse direction with programmable load current rising and falling slopes to induce a recognizable back electromagnetic force at a receiver emulating the magnetic strip data during the load current rising and falling portions and to reduce power loss during time periods without signal transmission.

Description

Magnetic strip data transmission system and reliable data transmission and low power consumption method

The present invention is primarily directed to systems and methods for directly transmitting magnetic stripe data to ensure reliable transmission of magnetic stripe data with low power consumption. More specifically, the present invention uses pulse width modulation in a magnetic stripe data drive. The method drives the switch of the magnetic stripe data driver to control the current ramp of the signal generated in the magnetic stripe transmission driver for low power and reliable data transmission.

Magnetic stripe data transmission or magnetic security transmission (MST) technology consists in that it is similar to the magnetic signal of the magnetic stripe data of a conventional payment card, transmitted from the transmitter to the receiver by an MST driver. The transmitter can be a host device such as a smart phone. The receiver can be a card reader of the payment terminal. The magnetic signal analogy reads the magnetic stripe data of the payment card normally read by the card reader, and physically pays the card on the card reader.

Figure 1 is a diagram showing the payment card data on the magnetic strip of the payment card. The card reader head of the payment terminal collects the waveform corresponding to the magnetic stripe data, and simultaneously pays the card along the digital equivalent of the waveform. The MST driver emits a magnetic signal that is analogous to the same waveform as the payment terminal reader, without paying for the card.

In conventional magnetic stripe data transmission or magnetic security transmission (see U.S. Patent No. 8,814,046), an MST driver is configured to transmit magnetic stripe data containing a pulse stream. The MST driver preferably includes a full bridge switch structure connected to the voltage source and ground to drive the bidirectional load current through the inductor based on the magnetic strip data. The MST driver transmits the magnetic signal to the card reader. During the transmission of the magnetic signal, the magnetic flux density of the inductor is changed according to the load current density, the inductance value and the load current gradient of the inductor, and a back electromagnetic force (B _emf ) is introduced at the distal end of the reader of the card reader. If the back electromagnetic force (B _emf ) is above the threshold, the reader recognizes it as a high pulse. If B _{emf is} below another threshold, the reader recognizes it as a low pulse. The high and low pulse combinations reconstruct the read head waveform of the reader.

Figure 2A shows a circuit diagram of an MST driver. The MST driver includes four MST drive switches 101, 102, 103, and 104, configured in a full bridge configuration, connected to a voltage source V _{M ·} 108 and a ground. The MST coil 105 is molded by the inductor 106 having an inductance of L ₁ and the series resistor R _{1 ·} 107. Each MST drive switch includes a respective diode (D1-D4) coupled to each of said switches to function as a free current path for storing energy in the inductor 106 during the turn-off process.

The MST drive switches 101, 102, 103, and 104 are driven by an external or built-in drive integrated circuit (IC). They have a pulsed drive waveform with a constant frequency or approximately 50% duty cycle of double frequency. In the MST driver, the first switch 101 and the fourth switch 104 are simultaneously turned on to drive the load current in the MST coil 105 in the forward direction. Both the second switch 102 and the third switch 103 are turned on at the same time to reverse drive the load current in the MST coil 105.

Figure 2B shows the switch drive operation of the MST driver and the corresponding load current waveform. The waveform can be divided into 6 segments of duration T1, T2, T3, T4, T5 and T6. The durations T1, T2, and T3 may be forward drive times. At durations T1, T2 and T3, the load current is positive. The durations T4, T5 and T6 can be reverse drive times. At durations T4, T5 and T6, the load current is negative. Positive or negative values depend entirely on the designer's preferences.

In FIG. 2B, the first switch 101 and the fourth switch 104 are turned on. During the T1 period, the load current increases, approaching the positive peak current. In the T3 period, the first switch 101 and the fourth switch 104 are turned off, and the second switch 102 and the third switch 103 are turned on. The load current begins to drop rapidly, but it is still positive. This phenomenon is called reverse breakdown. In the ON state of the second switch 102 and the third switch 103, the load current becomes a negative value during the T4 period. In the T4 period, except for their negative negative values, the load current slope and absolute peak are the same as T1. During the T5 period, the negative peak current continues to flow. In the T6 period, the second switch 102 and the third switch 103 are turned off, and the first switch 101 and the fourth switch 104 are turned on. The load current begins to drop rapidly, with the same slope as T3 except for the reverse case.

。負載電流

隨

的功率指數增大，其中L₁ 為MST線圈的電感值。與之類似，如果相同的訊號驅動第二開關102和第三開關103接通，則MST線圈105上的負載電流

隨

的功率從之前的電流開始增大，增大到峰值電流I_P 。Figure 2C shows the switching period of the MST drive switch, the corresponding load current waveform in the MST coil, and the back electromagnetic force (B _emf ) produced by the reader receiver. When the same signal drives the first switch 101 and the fourth switch 104 to be turned on, the load current I _L on the MST coil 105 increases from the previous current to the peak current I _P . The peak current I _P depends on the supply voltage of the voltage source V _{M ·} 108 and the series resistance R _{1 ·} 107 of the MST coil. If you ignore the series resistance of the switch, you can express it as

. Load current

With

The power index increases, where L ₁ is the inductance of the MST coil. Similarly, if the same signal drives the second switch 102 and the third switch 103 to be turned on, the load current on the MST coil 105

With

The power increases from the previous current and increases to the peak current I _P .

In FIG. 2C, since the generated B _{emf is} close to its peak value, the load current slope according to the B _emf waveform shown in FIG. 2C when the load current transient changes, and thus the first (I) and the second (II) of the load current. A short moment facilitates the transmission of magnetic signals. The steady-state period fixed to the +I _p or -I _p load current does not contribute to the generated B _emf . If the generated B _emf produces a voltage signal above the positive threshold voltage V _r at the receiver in the card reader, the card reader recognizes it as "high." If the generated B _{emf is} at a receiver in the card reader, generating a voltage signal below the positive threshold voltage -V _r , the card reader recognizes it as "low."

The back electromagnetic force (B _emf ) depends on the rate of change of magnetic flux density, following the rate of change of current density in the inductor. The rate of change of current density with time is basically the slope of the load current, which is inversely proportional to the inductance of the inductor. In the fast current slope, the generated B _{emf is} large. In the slow current slope, the resulting B _{emf is} small. In the fast current slope, if the corresponding duration is too short, the receiver in the reader may not recognize the signal. In the fast current slope for a long period of time, the peak induced current increases. It may exceed the rated current of the MST drive. High currents can cause additional power loss. High current slopes also have side effects such as noise and electromagnetic interference (EMI).

The optimization and control of the load current slope and duration is very important in MST drive technology, ensuring reliable signal transmission with less power consumption. However, in conventional MST drivers, the load current slope cannot be controlled except for changing the parameters of the coil inductance, the series resistance of the coil, or the on-resistance of the full bridge driver switch. Those parameters may not be easily controllable due to limitations such as performance, cost, and formation factors. One way is to increase the inductance of the MST coil, but the larger the inductance, the larger the size and the higher the cost. Therefore, the original technology of the MST drive cannot be completed. Due to the limited inductance, the prior art MST drivers have low energy efficiency. This takes a long time to receive good transmission quality. High efficiency may result in loss of signal.

The original technology of the MST driver is difficult to control or mediate, so its performance is affected by the power supply voltage and the MST coil. Regarding efficiency, the prior art method consumes a large amount of power even when there is no signal transmission. Signal transmission is only performed at the moment of load current. The steady state of the peak current consumes power when there is no operation. This is much longer than the transient time. Energy efficiency is even worse. Great impact on the power system.

It is necessary to propose a new MST driver that can program or control the load current slope value and duration to ensure low power consumption and reliable signal transmission.

In an example of the invention, a magnetic strip data transfer (MST) driver is proposed. The advantages of MST drivers include low power consumption and reliable transmission of magnetic signals.

Configure the MST driver to transfer the magnetic stripe data containing the pulse stream. The MST driver includes a pair of high side switches and a pair of low side switches. The pair of high side switches includes a first switch and a second switch. The pair of low side switches includes a third switch and a fourth switch. The first, second, third and fourth switches are arranged in a full bridge configuration connected to the voltage source and the ground. The inductor is connected to the output of the full bridge structure of the switch.

A switch driver is configured to drive the pair of low side switches and the pair of high side switches, utilizing pulse width modulation under current slope control to introduce an identifiable back electromagnetic force at the receiver. It is analogous to magnetic stripe data when the load current rises and falls through the inductor.

In an example of the present invention, a switch driver of the MST driver is configured to drive the pair of low side switches and the pair of high side switches to selectively and repeatedly switch in the on and off states. In the forward or reverse direction, the load current containing the rising and falling portions of the inductor is driven, and the programmable load current rise and fall slopes are utilized to generate a magnetic signal to introduce an identifiable back electromagnetic force at the receiver. In the load current rise and fall, the analog magnetic stripe data reduces power consumption when there is no signal transmission.

In an example of the invention, the switching drive of the MST driver includes configuring pulse width modulation to generate a first pulse width modulation (PWM) control signal for reliable data generation to generate a second PWM control signal for reducing power loss.

In an example of the present invention, a switch drive of the MST driver is configured to drive the pair of low side switches to control the load current so that in the continuous on state, the first switch is used to pass the rising portion and the falling portion of the inductor in the forward direction. And repeatedly switching the fourth switch between the on and off states according to the first PWM control signal and the second PWM control signal.

In an example of the present invention, a switch drive of the MST driver is configured to drive the pair of low side switches to control the load current so that in the continuous on state, the second switch is used to pass through the rising and falling portions of the inductor in the reverse direction. And repeatedly switching the third switch between the on and off states according to the first PWM control signal and the second PWM control signal.

In an example of the present invention, the switch driving of the MST driver is configured to drive the fourth between the on and off states according to the duty cycle of the first PWM control signal and the second PWM control signal, by repeatedly switching switch. Adjusting the duty cycle of the first PWM control signal, setting the rising portion of the forward load current to the current limit value of the forward first slope to generate a negative back electromagnetic force lower than the negative reference voltage in the receiver to identify the corresponding Low-pulse signal senses back electromagnetic force. Adjusting the duty cycle of the second PWM control signal to reach a current limit of the second slope, setting a falling portion of the forward load current, the second slope being opposite to the positive first slope and being slower than the positive first slope for receiving The positive back electromagnetic force is generated below the positive reference voltage, and the positive reference voltage is negligible to reduce power loss during periods of no signal transmission.

In an example of the present invention, the switch driving of the MST driver is configured to control the third between the on and off states according to the duty cycle of the first PWM control signal and the second PWM control signal, by repeatedly switching switch. Adjusting the duty cycle of the first PWM control signal, setting the falling portion of the reverse load current to the current limit value of the negative first slope to generate a positive back electromagnetic force higher than the positive reference voltage in the receiver to identify the corresponding The high-pulse signal senses the back electromagnetic force. Adjusting the duty cycle of the second PWM control signal to reach a current limit lower than the positive second slope of the first slope, controlling the falling portion of the reverse load current, the positive reference voltage can be neglected, so that during the period without signal transmission Reduce power loss.

In an example of the invention, a method for driving an MST driver is presented. Advantages of the method include low power consumption and reliable transmission of the MST driven transmit signal. Configure the MST driver to transmit the magnetic stripe data containing the pulse stream. The MST driver includes a pair of high side switches composed of a first switch and a second switch; a pair of low side switches composed of a third switch and a fourth switch. The first, second, third, and fourth switches are configured in a full bridge configuration, connected to a voltage source and ground. The inductor is connected to the output of the full bridge structure of the switch. The method utilizes a programmable load current rise and fall slope to generate a magnetic signal through the forward and reverse inductors by driving the load current with the rising and falling portions, producing an identifiable at the receiver The back of the electromagnetic force. In the load current rise and fall sections, the analog magnetic stripe data reduces the power loss during the no signal transmission period by controlling the slope of the current containing pulse width modulation (PWM).

In an example of the present invention, the method includes providing a plurality of diodes connected to the first, second, third, and fourth switches to facilitate free switching of the corresponding inductor coils in the off state of the switches The current that stores energy.

In an example of the invention, driving the load current through the inductor using the programmable load current rise and fall slopes includes selectively, repeatedly switching the pair of low side switches or the pair of high side switches.

In an example of the present invention, driving a load current through the inductive coil using a programmable load current rise and fall slope includes selectively and repeatedly switching the pair of low side switches including in a continuously on state, opening the first switch In the on and off states, the fourth switch is repeatedly switched, and the load current is driven forward using the programmable load current rise and fall slopes. It also includes turning on the second switch in the continuously on state, repeatedly switching the third switch in the on and off states, and driving the load current in reverse by using the programmable load current rise and fall slopes.

In an example of the present invention, driving a load current through the inductive coil using a programmable load current rise and fall slope includes selectively and repeatedly switching the pair of high side switches including, in a continuously on state, opening the fourth switch, In the on and off states, the first switch is repeatedly switched, and the load current is driven forward using the programmable load current rise and fall slopes. The method further includes turning on the third switch in the continuously on state, repeatedly switching the second switch in the on and off states, and driving the load current in the reverse direction by using the programmable load current rise and fall slopes.

In an example of the present invention, the method further includes driving the load current in a forward direction using the programmable load current rise and fall slopes, including the on and off according to the duty cycle of the first PWM control signal and the second PWM control signal. Repeat the toggle switch between disconnected states. Adjusting the duty cycle of the first PWM control signal, setting the rising portion of the forward load current to the current limit value of the forward first slope to generate a negative back electromagnetic force lower than the negative reference voltage in the receiver to identify the corresponding Low-pulse signal senses back electromagnetic force. Adjusting the duty cycle of the second PWM control signal to reach a current limit of the second slope opposite to the first slope and lower than the first slope, setting a falling portion of the forward load current to generate a lower than positive in the receiver The positive back electromagnetic force of the reference voltage, the positive reference voltage can be neglected to reduce power loss during periods of no signal transmission.

In an example of the present invention, the method further includes driving the load current in reverse by utilizing a programmable load current rise and fall slope, including switching on and according to a duty cycle of the first PWM control signal and the second PWM control signal Repeat the toggle switch between disconnected states. Adjusting the duty cycle of the first PWM control signal, setting the falling portion of the reverse load current to the current limit value of the negative first slope to generate a positive back electromagnetic force higher than the positive reference voltage in the receiver to identify the corresponding The high-pulse signal senses the back electromagnetic force. Adjusting the duty cycle of the second PWM control signal to reach a current limit lower than the positive second slope of the first slope, controlling the falling portion of the reverse load current, the positive reference voltage can be neglected, so that during the period without signal transmission Reduce power loss.

In an example of the invention, a positive first slope is selectively obtained to provide a load current rise time sufficient to introduce back electromagnetic force into the receiver as a low pulse signal.

In an example of the invention, a negative first slope is selectively obtained to provide a load current rise time sufficient to introduce back electromagnetic force into the receiver as a high pulse signal.

In the example of the present invention, the load current through the inductor is driven using a programmable load current rise and fall slope, including an intermediate phase between forward and reverse current drive. In order to achieve better power efficiency, the load current in the intermediate stage drops to zero.

In the example of the present invention, the linearity of the load current rise and fall slopes can be controlled by changing the duty cycle of the PWM control signal. For linear slopes, the PWM duty cycle can be changed. For a non-linear log slope, the PWM duty cycle is constant.

In the example of the invention, the PWM switching frequency is much greater than the input signal frequency during the rising and falling current slope intervals to reduce current ripple in the load current.

In an example of the invention, the method further includes a pulse frequency modulation (PFM) method including continuous on-time control and continuous off-time control to control the load current slope.

An MST driver and a method for driving an MST driver are proposed. Pulse width modulation (PWM) technology is used to control the current slope of the transmitted signal for low-power, reliable transmission of the transmitted signal of the MST driver. Configure the MST driver to transfer magnetic stripe data with high or low pulses. The MST driver includes a pair of high side switches composed of a first switch and a second switch, and a pair of low side switches composed of a third switch and a fourth switch. Configure the switch in a full-bridge configuration to connect to the voltage source and ground. The inductor is connected to the output of the full bridge structure of the switch.

The MST driver also includes a switch driver that uses PWM to drive the pair of low-side and high-side switches under current-slope control. In the rising and falling portions of the load current, an identifiable back electromagnetic force ((B _emf )) is introduced at the receiver through the inductive coil for analog magnetic stripe data.

The introduced back electromagnetic force _Beff is the time constant of the load current passing through the inductor. The introduced B _emf is a negative value of the load current. The introduced B _emf is calculated by the following formula:

為通過電感線圈的負載電流的時間常數，

對應負載電流斜率。Where L ₁ is the inductance value of the inductor coil,

The time constant of the load current through the inductor,

Corresponding to the slope of the load current.

The switch driver of the MST driver includes a pulse width modulator configured to generate a first pulse width modulation control signal (PWM 1) and a second pulse width modulation control signal (PWM 2). The switch driver drives the pair of low side switches or the pair of high side switches by selective, repeated switching between the on and off states. In the forward or reverse direction, the load current containing the rising and falling portions of the inductor is driven, and the magnetic signal is generated using the programmable load current rise and fall slopes. Introduce an identifiable back electromagnetic force at the receiver, analogous to the magnetic stripe data in the load current rise and fall sections.

A method of controlling the on-time or off-time of a drive switch using PWM to change the average current in the inductive load of the MST driver. Control the on-time or off-time of the MST drive switch, and program the current slope according to the requirements of the application. This method can transmit signals more reliably and efficiently. This method illustrates how to control or program the current slope steadily even with different supply voltages and MST coils by PWM control.

Figure 3 shows the MST switch drive mechanism of the full bridge switch structure of the MST driver in an example of the present invention. The MST driver includes a pair of high side switches 201, 202 and a pair of low side switches 203, 204 configured in a full bridge configuration connected to a voltage source V _{M ·} 208 and ground. The inductor MST coil 206 has an inductance L ₁ and a series resistor R _{1 ·} 207. Each MST drive switch includes a separate diode (D1-D4) connected by switches 201, 202, 203, 204. When the switch is turned off, it functions as a current path for freely switching the energy stored in the inductor MST coil 206. In an example of the invention, the full bridge switch structure of the MST driver includes first and second high side low side metal-oxide semiconductor field effect transistor (MOSFET) pairs connected in parallel between the voltage source and ground. Each high-side low-side MOSFET pair includes a high-side MOSFET and a low-side MOSFET in series with the drain of the high-side MOSFET, the high-side MOSFET is connected to the voltage source, the source of the low-side MOSFET is connected to ground, the inductor MST coil 206 and the series resistor R _{1 ·} 207 is connected between the common (output) nodes of the two high-side low-side MOSFET pairs.

The MST switch driving method shown in Figures 3(i)-(iv) proposes to selectively switch between a pair of low-side switches 203, 204 of the MST driver by using a programmable load current rise and fall slope. The positive and negative inductors contain load currents for the rising and falling portions. Each switch is driven by a separate drive signal that is different from each other.

In the MST driver, the first switch 201 for positively driving the load current in the MST coil is continuously turned on, and the fourth switch 204 is repeatedly switched in the on and off states. The second switch 202 for driving the load current in the MST coil in the reverse direction is continuously turned on, and the third switch 203 repeats the switching in the on and off states according to the duty cycle of the PWM control signal.

Figure 4 shows the switching operation of the MST driver at the receiver end using the load current waveform and the introduced back electromagnetic force in the example of the present invention. The waveforms have the same period P ₀ and are divided into six time periods T ₁ , T ₂ , T ₃ , T ₄ , T ₅ and T ₆ . The time periods T ₁ and T ₂ correspond to a "forward switch". The time periods T ₄ and T ₅ correspond to "reverse switches". The second slope (Slop2) ₅ between a first time period T ₁ and the current slope between T ₄ (Slop1) much larger than the period T, and T _2.

Referring to FIG. 3 (i) and FIG. 4, during time period T _1, a first switch 201 is turned on, according to a first duty cycle of the PWM control signals PWM 1, between the on and off states, switching the fourth repeat Switch 204. The other two switches 202, 203 remain in the off state. In the period T _1, a method using PWM 1, the load current (I _L) is increased to limit the load current excess current limit I _{L_lim.}

The PWM 1 repeatedly switches the fourth switch 204 between the on and off states in accordance with the duty cycle (on time). When approaching I _{L_lim} , the duty cycle increases to the maximum current. PWM 1 controls the forward load current to rise to the current limit value in the first positive slope Slop 1. Determine the value of Slop 1 and ensure that the negative back electromagnetic force (-V _fast ) introduced is lower than the negative reference voltage (-V _r ) at the end of the receiver. Therefore, the receiver can recognize the introduced back electromagnetic force based on the low pulse signal.

Another factor in successful transmission is that the Slop 1 duration T _lo should be long enough to identify the introduced back electromagnetic force in the card reader. In the MST driver, Slop 1 is controlled by setting the duty cycle of PWM 1. Transient load current during PWM control signal with small sawtooth waveform fluctuations. However, the load current I _L waveform shown in FIG. 4 shows the average value of the load current in the PWM.

At time T ₁ during the period, the load current reaches I _{L_lim,} begins to decrease, during the period T _2, the second PWM control signal PWM 2 controls the second current slope (Slop2). In the period T _2, FIG. 3 (ii) and, the fourth switch 204 is still switched between on and off states in FIG. 4, but which differs from the duty cycle T _1. PWM 2 makes the second slope (Slop2) opposite Slop 1 and well below the value of Slop1. Therefore, the introduced positive back electromagnetic force (V _slow ) is much lower than the positive reference voltage (V _r ) in the receiver and is ignored by the receiver. This operation significantly reduces power consumption compared to the prior art. In the conventional operation, for the time period T ₂ , the load current is fixed to a stable value, and a large amount of power (Iout*V _M ) is also consumed when not working.

The Slop2 and terminal current levels depend on the coil inductance value (L ₁ ), the peak current level (I _{L_lim} ) and the period (P ₀ ), and the reader reference voltage level (V _r ) of the reader. The terminal current level can or cannot reach zero. Set the duty cycle of PWM2 to control Slop2.

If the previous _3, the load current is attenuated completely in FIG. 3 (II) represented by the time period T, in the time period T _3, the load current is zero, the fourth switch 204 and second switch 202 and third switch 203 are turned off . The first switch 201 can be turned on or off. If the time period T the current in the load ₃ does not exist and skips, then the time period T ₂ starts after the time period T _4. The longer the T ₃ time, the better the power efficiency.

As shown in Fig. 3 (iii) and Fig. 4, the time period T _{4 is the} same as the time period T ₁ except that the direction of the load current is reversed. During the time period T ₄ , the first switch 201 and the fourth switch 204 are turned off. The second switch 202 is continuously turned on. According to PWM1, the third switch 203 is switched between the on and off states. During the time period T ₄ , the first slope Slop1 is negative and the introduced back electromagnetic force is positive. The positive back electromagnetic force (+V _fast ) should be higher than V _r and the time (T _hi ) should be long enough for the receiver to recognize the high pulse signal.

As shown in Fig. 3 (iii) and Fig. 4, the time period T _{5 is the} same as the time period T ₂ except that the direction of the load current is reversed. During the time period T ₅ , the first switch 201 and the fourth switch 204 are continuously disconnected. The second switch 202 is turned on. According to PWM2, the third switch 203 is switched between the on and off states. Compared with the period T _4, a second positive slope Slop2, the back electromagnetic force (-V _slow) is introduced into the negative and higher than -V _r, at the end of the receiver may ignore -V _r. In the example of the invention, all operations of T ₅ are the same as T ₂ except for the opposite directions.

The time period T ₆ shown in Fig. 3 (iv) and Fig. 4 is the same as the time period T ₃ .

As described above, in the MST driver switch driving operation, when the first switch 201 and the fourth switch 204 or the second switch 202 and the third switch 203 are turned on, the load current I _L level increases, for the on-period period t _on For the switch, Equations 1 and 2 are calculated:

……………………………..方程式1

................................... Equation 1

…………………………….方程式2

.................................. Equation 2

Where V _M is the supply voltage and L ₁ is the inductance of the MST coil. R ₁ is the series resistance of the coil. R on 1, ₂ is the on- _resistance of the high-end first switch 201 or the second switch 202. _R on4,3 fourth low-end switch 204 or third switch 203 of the on-resistance.

When the first switch 201 or the second switch 202 is turned on, and the fourth switch 204 and the third switch 203 are turned off, the current is lowered for the off period, which is calculated by Equations 3 and 4. This cycle is called free switching.

………… 方程式3

............ Equation 3

……….方程式 4

.......... Equation 4

Where V _F2,1 is the forward voltage of D2 or D1, and R _on2,1 is the on- _resistance of the high-end second 202 or first 201.

Figure 5a shows the power consumption of the reduced MST driver. In the prior art method, since the signal transmission occurs during the transient period of the load current, the steady state of the load current consumes a large amount of power when not operating. Therefore, the longer the time P ₀ , the greater the power loss consumed and the higher the temperature reached. In a battery system, the battery will be recharged more frequently.

In Figure 5b, during the time periods T ₂ and T ₅ shown in Figure 4, the load current is attenuated to zero. Therefore, if the time periods T ₃ and T ₆ are long, the average power loss P loss — _avg is at least half lower than that of the conventional MST driver.

In the prior art method, the slope changes rapidly at the beginning of the transmission, and the efficiency is out of control due to the free switching operation and the high voltage applied to the inductor (V _M +2VBE). A large amount of high frequency noise containing EMI is generated, resulting in various side effects. However, since the MST driver can control the current slope, an optimum state between performance and noise can be obtained.

The MST driver includes the use of linear and non-linear (logarithmic) rise and fall in the PWM load current. The PWM duty cycle based on the slope of the current can be controlled to linear or non-linear. The slopes of the rising and falling currents shown in Figure 4 are linear. For linear slopes, the PWM duty cycle changes. However, if the PWM duty cycle is constant, the rising and falling current slopes become non-linear (logarithmic).

In the fast/slow rising/falling current slope periods T ₁ , T ₂ , T ₄ and T ₅ , the PWM switching frequency is set much faster than the input signal frequency 1/P ₀ to minimize current fluctuations in the load current.

For successful signal transmission, the absolute values of |Slop1| and |Slop2| are determined by V _r , -V _r , T _hi and T _lo . Designing |Slop1| for B _emf to introduce the receiver, generating a voltage signal below V _r can be ignored. Referring to V _r and –V _r , |Slop1| is much higher than |Slop2|. |Slop1| is controlled for more successful data transfer, |Slop2| for reducing power loss.

Figure 6 shows the PWM switches of the high side switches 201, 202 (compared to the low side PWM switches shown in Figure 4). Shows almost the same results as the low-side PWM switch.

The PWM method of the present invention can be replaced by a pulse frequency modulation (PFM) method with stable on-time control and stable off-time control. In the example of the present invention, the load current slope is controlled by the PFM method instead of the PWM method to obtain a waveform similar to that of FIG.

Figure 7 shows the switching operation of the MST driver using PWM in the rising current slope at the receiver end using the load current waveform and the introduced back electromagnetic force in the example of the present invention. The switch driver includes a pulse width modulator configured to generate the first PWM control signal, PWM1 of Slop1. Only for more successful data transfer.

Figure 8 shows the switching operation of the MST driver in the example of the present invention using PWM in the falling current slope at the receiver end using the load current waveform and the introduced back electromagnetic force. The switch driver includes a pulse width modulator configured to generate the second PWM control signal, PWM2 of Slop2. Used only to reduce power loss.

Those skilled in the art will appreciate that there may be modifications to the embodiments described herein. For example, the time interval may vary. Other modifications, all of which are within the scope of the patent application of the present invention, may be found by those skilled in the art.

101, 102, 103, 104, 201, 202, 203, 204‧‧ ‧ switch
105‧‧‧MST coil
106‧‧‧Inductors
107, 207‧‧‧ series resistor
108, 208‧‧‧ voltage source
206‧‧‧Inductive MST coil
B _emf ‧‧‧back electromagnetic force
D1-D4‧‧‧ diode
I _L ‧‧‧Load current
I _P ‧‧‧peak current
I _{L_lim ‧‧‧current} limit
P ₀ ‧‧‧ cycle
PWM 1, PWM 2‧‧‧ control signal
P _{loss_avg ‧‧‧Average} power loss
Slop1, Slop2‧‧‧ slope
T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , T ₆ ‧ ‧ time period
T _lo , T _hi ‧‧‧Time
V _r ‧‧‧ positive threshold voltage
V _fast , V _slow ‧‧‧back electromagnetic force

Figure 1 shows the magnetic stripe data collected by the card reader of the payment terminal, along with the digital equivalent of the waveform, the payment card data description and the waveform of the payment card on the magnetic strip of the payment card.

Figure 2A shows a circuit diagram of an MST driver.

Figure 2B shows the switching period of the MST driver's inductor, the conventional MST drive switch and the corresponding load current waveform.

Figure 2C shows the switching period of the MST drive switch, the corresponding load current waveform in the MST coil and the inductive back electromagnetic force (Bemf) of the reader receiver.

Figure 3 [from (i) to (iv)] shows the switching drive mechanism of the MST driver in the full-bridge switching structure of the MST driver in the example of the present invention.

Figure 4 shows the switching operation of an MST driver with a load current waveform and a back electromagnetic force introduced at the receiver in an example of the present invention.

Figures 5a and 5b show the power consumption comparison of a prior art MST driver and the MST driver.

Figure 6 shows a comparison of the PWM switches of the high side switches 201, 202 with the low side PWM switches shown in Figure 4.

Figure 7 shows the switching operation of an MST driver with a load current waveform and a back electromagnetic force introduced at a receiver containing PWM in the rising current slope, only in the example of the present invention.

Figure 8 shows the switching operation of an MST driver with a load current waveform and a back electromagnetic force introduced at a receiver containing PWM in a falling current slope, only in the example of the present invention.

201, 202, 203, 204‧‧ ‧ switch

206‧‧‧Inductive MST coil

207‧‧‧ series resistor

208‧‧‧voltage source

D1-D4‧‧‧ diode

I _L ‧‧‧Load current

Claims (20)

A magnetic strip data transmission driver for transmitting magnetic stripe data containing a pulse stream, the magnetic strip data transmission driver comprising: a pair of high side switches including a first switch and a second switch; and a pair comprising a third switch and a fourth switch Low-side switch; the first, second, third, and fourth switches are configured in a full-bridge configuration to be connected to a voltage source and ground; an inductor is coupled across the output of the full-bridge configuration of the switch; and a switch a driver for driving the pair of low-side switches and the pair of high-side switches to control the load current slope of the rising and falling portions of the load current, generating back electromagnetic force, passing the inductor coil in the rising and falling portions of the load current, analog magnetic stripe data . The magnetic stripe data transmission driver of claim 1, wherein the pair of low-side switches or the pair of high-side switches are selectively switched between on and off states by configuring a switch driver to control the load. The current, in the forward or reverse direction, is generated by the inductor to produce a rising portion and a falling portion to have a programmable load current rise and fall slope to generate a magnetic signal at the load current rising and falling portions. The magnetic stripe data transmission driver of claim 1, wherein the switch driver generates a first control signal for reliable data generation and generates a second control signal for reducing power loss. The magnetic stripe data transmission driver of claim 3, wherein the first switch is set in a continuously on state, and the fourth switch is repeatedly switched in an on and off state, according to the first control The signal and the second control signal are configured to drive the pair of low side switches forward. The magnetic stripe data transmission driver of claim 4, wherein the switch driver is configured to repeatedly switch between the on and off states according to the duty cycle of the first control signal and the duty cycle of the second control signal. a four-switch; wherein the duty cycle of the first control signal is adjusted, and the rising portion of the forward load current not exceeding a predetermined current limit has a positive first slope to generate a negative back electromagnetic force, and a lower than one is generated in the receiver a negative reference voltage signal to identify the generated back electromagnetic force corresponding to the low pulse signal; and wherein the duty cycle of the second control signal is adjusted, and the forward load current is set to fall after reaching the predetermined current limit, having a second The slope, the second slope value is lower than the forward first slope value to produce a positive back electromagnetic force, and another signal below the positive reference voltage is generated in the receiver to reduce power loss when there is no signal transmission. The magnetic stripe data transmission driver of claim 3, wherein the switch driver is configured to set the second switch in the on state, according to the first control signal and the second control signal, in the on and off states The third switch is repeatedly switched between and the pair of low side switches are driven in reverse. The magnetic stripe data transmission driver of claim 6, wherein the switch driver is configured to repeatedly switch between the on and off states according to the duty cycle of the first control signal and the duty cycle of the second control signal. a three-switch; wherein the duty cycle of the first control signal is adjusted, and the falling portion of the reverse load current not exceeding a predetermined current limit has a negative first slope to generate a positive-back electromagnetic force, which is generated higher than one in the receiver Positive reference voltage signal to identify the generated back electromagnetic force corresponding to the high pulse signal; and wherein the duty cycle of the second control signal is adjusted, and the rising portion of the reverse load current after reaching the current limit is set to have a positive second slope , the absolute value of the forward second slope is lower than the absolute value of the negative first slope to generate a negative back electromagnetic force, and another signal higher than a negative reference voltage is generated in the receiver to be reduced when there is no signal transmission Power loss. A method for driving a magnetic stripe data transmission drive with reliable signal transmission by a low power, magnetic strip data transmission driver, the method comprising the steps of: providing a pair of high side switches including a first switch and a second switch; a pair of low side switches including a third switch and a fourth switch; the first, second, third and fourth switches are configured in a full bridge configuration, connected to the voltage source and ground; providing an inductive coil connected to the switch The output of the bridge structure; driving the load current with the rising portion and the falling portion, passing the inductor in the forward or reverse direction, using the programmable control of the load current rise and fall slope to produce an identifiable back electromagnetic at the receiver Force, analogous to the magnetic stripe data in the load current rise and fall, and use pulse width modulation to control the programmable load current rise and fall slopes when there is no signal transmission, reducing power loss. The method of claim 8, further comprising providing a diode connected to each of the first, second, third and fourth switches so as to be in accordance with the inductor coil when the switch is opened The stored energy is free to switch the load current. The method of claim 8, wherein the programmable load current rise and fall slopes are used to drive a load current through the inductor to generate a magnetic signal, including selectively repeating switching the pair of low side switches or the pair High-end switch. The method of claim 10, wherein selectively switching the pair of low-side switches or the pair of high-side switches comprises: setting the first switch to be repeated in an on-and-off state in a continuously on state Switching the fourth switch, using the programmable load current rise and fall slopes, driving the load current in the forward direction; and setting the second switch to continuously switch the third switch in the on and off states in the continuous on state, Program the load current rise and fall slopes to drive the load current in reverse. The method of claim 10, wherein selectively switching the pair of low-side switches or the pair of high-side switches comprises: setting the fourth switch to be repeated in the on and off states in the continuously on state Switching the first switch, using the programmable load current rise and fall slopes, driving the load current in the forward direction; and setting the third switch to continuously switch the second switch in the on and off states in the continuous on state, Program the load current rise and fall slopes to drive the load current in reverse. The method of claim 8, wherein the load current through the inductor is driven by the programmable load current rise and fall slopes to generate a magnetic signal, including a duty cycle according to the first PWM control signal and a second PWM Controlling the duty cycle of the signal, repeating the switching between the on and off states, including: adjusting the duty cycle of the first PWM control signal, setting the rising portion of the forward load current not exceeding a predetermined current limit to have a positive direction a first slope to generate a negative back electromagnetic force, generating a signal lower than the negative reference voltage in the receiver to identify the generated back electromagnetic force corresponding to the low pulse signal; and adjusting the duty cycle of the second PWM control signal, setting the positive To a falling portion of the load current after reaching the predetermined current limit, having a second slope, the second slope value being lower than the forward first slope value to generate a positive back electromagnetic force, generating a lower than positive reference voltage in the receiver Another signal to reduce power loss when there is no signal transmission. The method of claim 13, wherein the positive first slope is selected to provide a sufficient period of time for the load current to rise, and the signal generated by the negative back electromagnetic force is identified as a low pulse signal in the receiver. The method of claim 8, wherein the load current through the inductor is driven by the programmable load current rise and fall slopes to generate a magnetic signal, including a duty cycle according to the first PWM control signal and a second PWM Controlling the duty cycle of the signal, repeating the switching between the on and off states, including: adjusting the duty cycle of the first PWM control signal, setting the falling load current to a falling portion of a predefined current limit, having Negating the first slope to generate a positive back electromagnetic force, generating a signal higher than the positive reference voltage in the receiver to identify the generated back electromagnetic force corresponding to the high pulse signal; and adjusting the duty cycle of the second PWM control signal, Setting a rising portion of the reverse load current after reaching the current limit, having a positive second slope, the absolute value of the positive second slope being lower than the absolute value of the first slope to generate a negative back electromagnetic force, generating a high in the receiver Another signal of negative reference voltage to reduce power loss when there is no signal transmission. The method of claim 15, wherein the negative first slope is selected to provide sufficient time for the load current to fall, and the signal generated by the positive back electromagnetic force is recognized as a high pulse signal in the receiver. The method of claim 8, wherein the intermediate stage is between forward and reverse, wherein the load current drops to zero in the intermediate stage to improve power efficiency. The method of claim 8, wherein the linearity of the load current rise and fall slope is controlled by changing the duty cycle of the PWM control signal; wherein for the linear slope, the PWM duty cycle is varied, wherein For linear log slopes, the PWM duty cycle is constant. The method of claim 8, wherein the PWM switching frequency is higher than the input signal frequency at the rising portion and the falling portion of the load current to reduce the chopping of the load current. The method of claim 8, further comprising a pulse frequency modulation method comprising fixed on-time control and fixed off-time control to control load current rise and fall slope.